The present invention relates to communications technology, particularly to satellite communications using a traveling wave tube. In addition, the present invention relates to a control apparatus in particular for a traveling wave tube, an earth-distant platform, particularly a satellite, having an apparatus according to the invention, as well as a method for setting an operating state of a traveling wave tube.
A traveling wave tube (TWT) is a highly specialized vacuum tube that is used for amplifying RF signals. Traveling wave tubes are particularly favored on earth-distant platforms, such as satellites, to provide RF signals for communications with a communications partner, for example an earth-proximate or ground station.
Accordingly, traveling wave tubes amplify the RF signal, whereby free electrons, which move in the tube from one cathode towards an anode and are then captured by collectors, release part of their kinetic energy as an electrical signal to be amplified. In doing so, traveling wave tubes preferably have a field of application in a frequency range from 0.3 to 50 GHz, wherein amplification is usually feasible in a range of 30-60 dB. Based on their high efficiency of up to 70%, traveling wave tubes particularly above 10 GHz are superior to semiconductor amplifiers.
For their operation, traveling wave tubes require a heating voltage for the hot cathode of several V to generate the electron beam, wherein the electrons are subsequently accelerated toward an anode and ultimately after passing through a region with a helical winding, they are captured by a collector. The traveling wave tube thus allows for energy recovery by means of the recovered electrons, which results in its relatively high efficiency.
In addition, an axial magnetic field generated by a permanent magnet or electromagnet is required as well as an operating voltage or accelerating voltage in the kV range. Also required are operating variables or operating energy variables, which may be used, for example, to control or focus voltages for the electron gun. In addition, cooling of the collector and often of the helix may be required, particularly for high-power applications. Especially in satellite technology, an electrical supply unit is referred to as an electronic power conditioner (EPC). A unit comprised of a TWT and an EPC is referred to as a traveling wave tube amplifier (TWT).
Traveling tube amplifiers are used primarily as power amplifiers in satellites. The traveling wave tube thus mainly determines the high-frequency properties. In addition, a power supply or a control apparatus for a traveling wave tube is provided, which generates the supply voltage for the traveling wave tubes and also represents a telemetry or telecommand interface to the satellite. A power amplifier can be supplemented by a preamplifier, also known as a channel amplifier (CAMP), which can also contain a linearizer (LCAMP). In such a combination, such an apparatus is referred to as a high-frequency power module (microwave power module (MPM)).
Besides the high-frequency design of the traveling wave tube itself, the supply voltages primarily determine the high-frequency properties of the traveling wave tube. These voltages are adjusted in such a manner that the required performance features can be maintained over a required frequency range. Particularly for large frequency ranges, a compromise must be found between the frequency range and requirements.
Generally, a setting of the traveling wave tube is made in such a manner that the center of the achieved frequency range is set so that also on the end and thus in the entire frequency range required, the specified requirements are complied with. In the central region, these requirements are usually greatly exceeded.
In very broadband applications, it may occur that absolutely no operating state can be found that is able to cover the entire frequency range. In this case, sub-regions must be covered by various amplifiers.
The preamplifier of an MPM must thus be adapted to the tube properties, i.e., when the characteristics of the tube change, the setting of the preamplifier must be adapted correspondingly.
One aspect of the present invention is now the setting of a control apparatus of an earth-distant platform for an RF transmit amplifier unit, particularly of an associated energy supply unit and/or an associated preamplifier or channel amplifier and/or linearizer in such a flexible manner that in the orbit, for a satellite application, various settings can be selected via telecommand, depending on which frequency range or frequency band the amplifier or the RF transmit amplifier unit is to be operated in.
Accordingly, a control apparatus for an earth-distant platform, an earth-distant platform, particularly a satellite, having an apparatus according to the invention, as well as a method for setting an operating state of an RF transmit amplifier unit are provided on an earth-distant platform according to the invention.
According to a first design of the present invention, a control apparatus for an earth-distant platform is disclosed, having a control unit with at least one control input and a control output and a memory element, wherein the memory element is arranged to store a plurality of operating value parameter sets for at least an RF transmit amplifier unit, wherein the control input is arranged to receive a control signal, wherein the control unit is arranged, based on the control signal, to select an operating value parameter set from the memory element, and wherein the control output is arranged, subject to using the selected operating value parameter set, to influence an energy supply unit and/or linearization element in such a manner that the RF transmit amplifier unit is operable in a certain operating state.
According to another design of the present invention, an earth-remote platform, particularly a satellite, having a control apparatus for a traveling wave tube, is disclosed.
According to another design of the present invention, a method for setting an operating state of a traveling wave tube, particularly an earth-distant platform, is disclosed, having the steps: receiving a control signal; selecting an operating energy value parameter set from a plurality of operating energy value parameter sets, which are stored locally in a memory element; and adjusting the operating state of the traveling wave tube, based on the selected operating energy value parameter set.
According to a first design of the present invention, a control apparatus for an RF transmit amplifier unit is disclosed, having an energy supply unit, wherein the energy supply unit is arranged to provide a plurality of operating energy values defining an operating energy value set to a traveling wave tube, wherein the operating energy value set determines an operating state of the traveling wave tube, wherein a plurality of operating states can be determined by means of a plurality of operating energy value sets, and a control unit, wherein the control unit has at least a control input, a control output, as well as a memory element, wherein the memory element is arranged to store a plurality of operating energy value parameter sets, wherein each operating energy value parameter set is associated with an operating value set and wherein by means of selecting a certain operating energy value parameter set, a certain operating energy value set of the energy supply unit can be adjusted in such a manner that the traveling wave tube is operable in the associated defined operating state.
In addition, the present invention is described taking into account a traveling wave tube as an RF transmit amplifier unit. These designs however pertain to any RF transmit amplifier unit, particularly also to a semiconductor amplifier. If in addition an operating energy value set or operating energy value parameter set is described or used, this shall generally refer to an operating value set or operating value parameter set.
According to the invention, a control apparatus for a traveling wave tube, thus an electronic power conditioner, is provided for actuating and for operating a traveling wave tube. It can have, but is not required to have, a channel amplifier and/or a linearizer and thus essentially can represent a microwave power module.
By way of example in the case of a satellite application, the control apparatus obtains, for example, a command from a ground station regarding a desired operating mode of the traveling wave tube. In addition to other possible information, this may include in particular information regarding on which frequency or in which frequency band the traveling wave tube or the traveling wave tube amplifier is to be operated.
It is hereby advantageous that no complex information is transmitted that contains detailed information or parameters regarding the setting of an energy supply module. Instead, only information is transmitted as to which frequency band is now to be used for the transmission. All parameters required for setting and operating the control apparatus and thus the traveling wave tube are on hand in a memory element in the control apparatus. These pieces of information or parameters may be provided beforehand by a manufacturer of the satellite or at least the traveling wave tube amplifier, so that one can ensure that the traveling wave tube implements the required transmission properties in the best possible manner. A corresponding plurality of parameter sets may have been determined in a test operation during production for example and stored in the memory.
Thus, essentially only one piece of information is transmitted as a telecommand, indicating that the traveling wave tube amplifier is to now operate in a certain frequency band, Possibly, a piece of information may also be transmitted as to which modulation procedure is to be used for the data transmission. In doing so, these two pieces of information, which can be transmitted with comparatively little data volume to an earth-distant platform, may access in particular extensive parameter data in the memory element to best operate or parameterize the traveling wave tube, taking into consideration the required transmission in each case.
By transmitting purely a piece of information, as to which transmission parameter set is now to be used from the memory element, and not for example (complex) control data or parameters themselves that directly execute the parameterization of an EPC, one also ensures that the traveling wave tube amplifier is operated exclusively with a complete and correct parameter set, which was desired, required, and tested in particular.
If for example the parameters themselves are transmitted via a telecommand from an earth station to a satellite and if in doing so a transmission error occurs, it may happen that all or some parameters are not correctly set, possibly do not fit with other parameters, and thus a transmission based on an incorrect setting of the traveling wave tube is no longer possible. In a worst case scenario, this could result in damage to the traveling wave tube amplifier or the traveling wave tube, which in the event of a catastrophic defect could ultimately result in the total failure of the amplifier.
This is effectively prevented by the transmission of simple instructions via telecommands as to which transmission mode is to be selected, with a subsequent selection of this mode from a memory element, and the setting of all relevant parameters, based on this selected memory element. Based on a possible data transmission error when transmitting the telecommand, a non-desired mode could be set; however it would then take into account all correct parameters for this mode so that at least catastrophic damage of satellite elements is effectively prevented.
In this way, one can determine that the traveling wave tube amplifier can be operated in an optimal operating state by selecting a parameter set from the memory element. This results for example in improved efficiency and thus in better use of existing power. In the event of a satellite, it may thus be possible to construct it in a more cost-effective manner.
Storing a plurality of parameter sets allows one to set a plurality of frequency ranges with one device, for which if there was no adjustment capability, two or even more apparatuses would be required. In this way, the number of apparatuses stored in the satellite may be reduced and/or simpler redundancy concepts may be designed.
If, for example, multiple TWTAs/MPMs are provided in a satellite, then each TWTA/MPM can cover the entire frequency range. For that reason, each TWTA/MPM can be operated at each frequency of the redundancy concept, which simplifies the redundancy concept in certain circumstances.
According to the invention, a control unit on the satellite-side is provided that, based on a telecommand, selects from the memory element a desired or required operating energy value parameter set from a plurality of operating energy value parameter sets. Such an operating energy value parameter set defines all operating values, particularly in regard to the power supply and voltage actuation of a traveling wave tube, which are required to operate the traveling wave tube in a certain operating mode or operating state, and thus in a certain operating frequency band.
The operating energy value parameter set is thus to be considered as a piece of information, as to how the actual operating energy values, which are forwarded or applied to a traveling wave tube, are to be set. An energy supply unit of the control apparatus can thus be actuated by the controller in such a manner that, based on the information from the operating energy value parameter set, provides an energy value set and forwards or applies it to the traveling wave tube.
As an example, the operating energy value parameter set may contain a piece of information as to which anode voltage or cathode current is to be set for a certain operating state of the traveling wave tube. This information regarding the anode voltage is implemented, using the energy supply unit, in such a manner that the actual real anode voltage or cathode current associated with this information regarding the anode voltage or cathode current is generated and provided or applied to the traveling wave tube.
According to a preferred design of the present invention, the control input of the control unit can be arranged to receive a control signal for selecting a certain operating state or a certain operating energy value parameter set, wherein the control unit, based on the control signal, selects an operating energy value parameter set from the memory element and wherein the control output is arranged, using the selected operating energy value parameter set, to influence the energy supply unit in such a manner to set or issue the associated operating energy value set.
According to another preferred design of the present invention, the traveling wave tube can take up a certain operating state by setting or outputting the energy supply unit by means of the operating energy value set to the traveling wave tube.
The control apparatus is thus arranged so as to implement, from a plurality of operating energy value parameter sets, the selected one in such a manner that the operating energy values associated with this operating energy value parameter set are forwarded or applied to the traveling wave tube to thereby set a defined or desired operating state of the traveling wave tube.
According to another preferred design of the present invention, the operating energy values or operating values may be designed as values from the group consisting of currents or voltages that can be applied or forwarded to an RF transmit amplifier unit (4), a helix voltage, a collector voltage, a cathode current, an anode-0 voltage, an anode-1 voltage, a heater voltage, a Wehnelt voltage, an amplitude expansion, a phase rotation, a frequency response, and an amplification.
To operate the traveling wave tube, a plurality of currents or voltages are necessary due to the construction. This plurality or the entirety of all voltages and/or currents required to operate the traveling wave tube and if applicable other parameters, e.g., regarding signal processing, represent the operating energy values that can be depicted for a desired operating state as an operating energy value set. Generally, the operating energy values are operating values. A linearization element (LIN) may adapt its pre-processing or its transmission characteristics based on an operating state and thereby adapt to an amplitude expansion, phase shift, frequency response, and an amplification. This also applies if the linearization element is combined with a channel amplifier (LCAMP) or if the preamplifier is solely a channel amplifier (CAMP), in other words if it does not contain a linearizer. In this case, in particular only the amplification and the frequency shift of an HF signal may adapted.
According to another preferred design of the present invention, an operating state of the traveling wave tube may influence or determine at least the frequency operating range of the traveling wave tube, thus a frequency range.
According to another preferred design of the present invention, the control apparatus may be combined with a preamplifier, which includes amplifier stages and a linearization element, with a high-frequency input and a high-frequency output, to which a traveling wave tube can be connected. The linearization element may thus be arranged to receive a high-frequency signal via the high-frequency input and preprocess it, taking into account a desired or required operating state of the traveling wave tube. In doing so, preprocessing may affect in particular a transmission characteristic of the linearization element and influence it, based on a certain or desired operating state. In particular, the operating energy value parameter set may also have a piece of information or a parameter for adjusting the linearization element to adapt it, in its preprocessing of the high-frequency signal or its transmission characteristic, to a defined or required operating state of the traveling wave tube.
In this way, the memory element may also contain a piece of information for a certain operating energy value parameter set as to how a channel amplifier and/or linearizer is to be set, taking into account the desired or required operating state, and thus in particular the frequency band of the traveling wave tube.
According to a preferred design of the present invention, a transmission channel may be adapted to a required modulation procedure for data transmission by means of a plurality of operating energy value parameter sets.
In other words, for various modulation processes, even in a same frequency band, various operating energy values may be needed to adapt the traveling wave tube in a particularly preferred manner to a modulation procedure. In this way, an operating energy value parameter set may not only adjust an operating state in relation to a frequency band, but in addition, it may also adapt or optimize the traveling wave tube to a certain modulation procedure.
According to another preferred design of the present invention, the memory element may be arranged in the control unit, in the energy supply unit, or in the preamplifier/linearizer or be constructed as a distributed memory element and be arranged in several of the following: control unit, energy supply unit and preamplifier/linearizer element.
In this way, the control unit may, as a combination of a control unit with an energy supply unit, be constructed as an EPC, also in combination with a channel amplifier/linearization element and constructed as a channel amplifier/linearization element without an RF transmit amplifier unit purely as a preamplifier and with an RF transmit amplifier unit, particularly a traveling wave tube, as a TWTA or MPM.
According to another preferred design of the present invention, the apparatus may have at least two RF transmit amplifier units, at least two linearization elements, and at least an energy supply unit, wherein an RF transmit amplifier unit is assigned to each linearization element, wherein the at least one energy supply unit is arranged to operate the at least two RF transmit amplifier units and wherein the memory element has operating value parameter sets for the at least one energy supply unit and the at least two linearization elements.
According to another preferred design of the present invention, the RF transmit amplifier unit may be constructed as a unit from the group consisting of traveling wave tube and semiconductor amplifier.
Hereby, a plurality, for example 2, 3, up to n RF transmit amplification units and associated linearization elements may be connected to an energy supply unit for achieving individual operating states.
According to another preferred design of the present invention, the control signal may be receivable from outside a platform, in particular emanating out from the earth's surface, for example in the case that the control apparatus according to the invention for a traveling wave tube is provided on an earth-distant platform, in particular a satellite.